Method of applying protective coatings to metallic articles.



CLARENCE MARK, 0F EVANSTON, AND CLAYTON MARK, JR., OFIIIAKE FOREST,ILLINOIS,

ASSIGNORS TO CLAYTON MARK, OF LAKE FOREST, ILLINOIS:

METHOD OF APPLYING PROTECTIVE COATINGS TO METALLIC ARTICLES.

1N0 Drawing.

To all whom it may concern:

Be it known that we, CLARENGE MARK, .residin at Evanston, in the countyof Cook and gtate of Illinois, and CLAYTON "MARK, J r., residing at LakeForest, in the county of Lake and State of Illinois, citizens of theUnited States, have jointly invented a new and Improved Method ofApplying Protective Coatings to'Metallic Articles, of which thefollowing is a specification.

Our invention relates to methods of applying protective coatings tometallic ar-' ticles, and consists in introducing the articles to becoated into a bath containing lead and zinc, or lead, tin and zinc insuch proportions that when they are alloyed they are electro-positive toiron in an electrolyte, such as tap water, salt solutions or commonconducting solutions other than nitrates, and in maintaining a suitableprotective flux upon the bath.

Our invention also consists in maintaining the bath at a temperaturelower than the melting point of zinc and in the periodic addition ofzinc which will be taken up by the bath so as to maintain constant theproportion of zinc in the alloy.

A typical example of carrying out our process is as follows:

We take the article to be coated, such as an articles of iron or steel,and cleanse it in a suitable bath, preferably using the usual sulfuricacid pickle, and, after washing the article, putting it through a bathcomposed of muriatic acid and sal-ammoniac, or zinc chlorid, or both,and water, such as is ordinarily used in a galvanizing process, the

article is then passed through molten bath of lead, tin and zinc coveredwith a salammoniac flux, in which flux ispresent zinc and iron in smallpercentages. By reason of the great afiinity of the zinc for iron orsteel,

the article immediately picks up small percentages of zinc, and the zincforms on the surface of the iron a zinc-iron alloy, to

which the composition of the bath will adhere. As soon as the articlehas reached approximately the temperature of the molten bath, which ispreferably between 650 and 7 F, the article is withdrawn from the moltenbath, and then is kept in motion until the coating has set, so as toprevent the coating from depositing unevenly.

The bath,is preferably of the following composition: Lead 94.45, zinc1.81, tin 3.74:,

Specification of Letters Patent.

sired proportion of zinc.

tures between 650 and 760 F. are used.

When the temperature is increased more zlnc may be added, orwhen thepercentage of tin is increased the higher is the percentage of zincwhich is necessary to saturate the bath.

The zinc vaporizes readily, and also, in addition to being taken up withthe other ingredients to form the coating on the article, it combineswith the iron of the articleto form a zinc-iron alloy and it also istaken up by the flux, so the bath becomes. depleted of its zlnc, unlessspecial steps are taken to prevent this. great importance to keep thequantities of zinc in the bath uniform, and, to this end, We add smallquantities of zinc at frequent intervals, to keep up the necessary:percentage, of this metal in the alloy, preferably near to PatentedSept. 28, 1915. 4

Application filed May as, 1914. Serial No. 841,484.

We have found that it is of saturation. The zinc is preferably added ina molten state, to facilitate. the ease with which it is dissolved inthe bath," and it is added and maintained in slight excess eof theamount desired to alloy with the other metal in the bath; thus the zinccollects around the edge of the pot and is automatically taken up by thebath asthe proportion of zinc in the alloy becomes depleted, and

the presence or absence of the free zinc serves as an 1nd1cat1on to theworkman as to Whether or not the 'alloy contains the de- By introducingthe zinc in a molten state we are enabled to maintain. the bath at atemperature below the melting point of zinc, which results not only insaving the cost of fuel, but in a saving in the zinc, since the zinc, ifmaintained at such-lower temperature, does not vaporize cooling and inthe production of a more uniform coating. To replenish the volume of thebath, lead, tin and zinc are added in the usual proportions.

Analysis and examination of an article coated with the coating describedabove has shown the coating to consist of an underlying layer of'azinc'iron alloy, which is cove .as readily as it would at a higher.tempera ture. This also results in a saving of time in cried andcombined with an alloy of lead,

tin and zinc, which forms the exterior coat- The alloy forms a smoothand uniform coat- 'ing, which can be readily applied topipes,

sheeting and similar articles, and it has been found to be very valuablein protecting iron castings, especially those which are malleableized.This coating, by reason of being applied to the articles at a lowtemperature, will not change the condition of the carbon content due tothe article having been malleableized.

It is obvious that various modifications may be made in the processwhich we have described and claim herein, without departing fromour'invention.

t is to be understood that in our co-pending applications, Serial No.760,903, filed .April 14, 1913, and Serial No. 43,528, filed August 4,1915, We have described and claimed articles'coated by the processdescribed herein. 7

What we claim is:

1. The herein described process of applying protective coatings tometallic articles, 'which consists in introducing the article to' becoated into a molten bath consisting of lead, with small percentages oftin and zinc, the zinc being present substantially, up to the point ofsaturation of the bath,the molten .metal being covered by a flux ofsalammoniac containing iron and zinc salts.

2. The herein described process of apply-' I ing a protective coating toiron and steel articles, which consists in introducing metallic articlesinto a bath, the temperature of which is between 650 and 760 F. and

being protected by a flux of sal-ammoniac containing iron and zincsalts, the said bath containing mainly lead, but having alloyed wlth itenough zinc to render the coating obtained from said bathelectro-positive to iron but not in excess of 3%- of zinc.

3. The herein described process of apply-- ing protective coatings tometallic articles, which consists 1n introducing the metallic articlesto be coated into a bath of lead con- 1 taining zinc heated to between650 to 7 60 F., and adding more zinc periodically so as to maintain theproportion of zinc in the alloy at a point below 3% but above an amountnecessary to render the coating formed from the bath electro-positive toiron. 4. The herein described process of applying protective coatings tometallic articles, which consists in introducing metallic articles intoa lead bath containing tin and zinc, covered with a fluX ofsal-ammoniac, said flux containing zinc and iron salts, the bath formingupon the surface of thearticles a zinc-iron alloy, and forming upon thezinciron alloy, an alloy of lead, tin and zinc.

5. The herein described process of applying a protective coating'tometallic articles, which -consists in introducing metallic articles intoa bath containing lead and zinc substantially up to the saturationpoint, and periodically adding zinc in such proportions as will maintainthe zinc content at a uniform percentage in the bath at temperaturesless than the melting point of zinc.

6. Process of coating iron articles, consisting in immersing them in alead bath maintained at a temperature between 650 and 760 F., said leadbath containing'tin under 7.5% and zinc substantially up to the point ofsaturation of thebath at the operating temperature, the maintenance ofthis zinc content being provided by the periodical addition of zincinsuch quantity that a por-' tion of it floats upon the surface and thusfurnishes an indication'as to the condition of the bath.-

7. The herein described process of applying a protective coating tometallic articles,

which consists in introducing articles into a bath containing lead andzinc substantially up to thesaturation point, and periodically addingzinc in such proportions as Wlll maintain the zinc content at a uniformpercentage in the bath. CLARENCE MARK.

CLAYTON MARK, JR. 1

